1. Field of the Invention
The present invention relates generally to ram air turbine generating devices and, more particularly, to an improved ram air turbine generator, which includes a unique air flow actuated air bypass valve, which together with the inlet diffuser, limits variations in the dynamic fluid power of the air flow passing through the turbine wheel, thereby limiting variations in fluid power transferred to the turbine blades. Operational capability for subsonic, transonic and supersonic flight is a primary feature of the invention.
2. Description of the Prior Art
It has long been a goal of designers of ram air turbine generating devices to minimize variations in turbine speed and power output of the generator and prevent generator overspeed and overheating. Failure to do so would require substantially greater design margins in the generator capacity to accommodate the complete range of altitude and flight speed of the flight vehicle in which the ram air turbine generator is mounted.
Also, in turbine devices, it is necessary to provide speed regulation to prevent a turbine wheel from attaining a speed at which the turbine disk or blades will fail. A common method which has been used in gas turbine engines to limit speed is that of absorbing power with a special turbine stage. This method has the disadvantage that efficiency losses result at normal operation conditions. Another method of speed control utilized a mechanical governor to detect excessive speed and this signal is used to actuate a control device which regulates the gas supply to the turbine. Even in gas turbine engine designs, it is apparent that a control which is more simplified than a governor-regulator system would be desirable.
One attempt at a simplified improvement is presented in U.S. Pat. No. 3,075,742 to Aldag which provided a turbine with a spring-biased shroud at the turbine blade tips so constructed that, at a predetermined speed, the shroud moves in response to reaction pressure forces and enables the gasses to move radially to give less effective gas flow for speed reduction.
More recent attempts to provide bypass valve assemblies for gas turbine engines are disclosed in U.S. Pat. Nos. 5,184,461 and 5,182,905 to Stransky et al., and 5,113,649 to Seidlecki, Jr.
Flow control devices associated with turbochargers are disclosed, for example, in U.S. Pat. No. 3,994,620 to Spraker, Jr., et al. and in UK Patent Application GB 2,059,515 to Melzer.
Other fluid driven turbine machines with fluid venting capability are disclosed in U.S. Pat. Nos. 5,083,723 to Grieb et al. and 3,504,986 to Jackson.
A common example of a fluid control device is disclosed in U.S. Pat. No. 3,386,368 to Fielding which is directed to a ventilator with a damper movable between open and closed positions.
It was in light of the state of the technology as just discussed that the present invention was conceived and has now been reduced to practice.